Hitherto, from the viewpoint of cost saving and energy saving, there has been a demand for reducing the amount of energy consumption in an HVAC device. In particular, when the HVAC device is driven by a battery, efficient air conditioning with small power consumption is demanded in order to use a small capacity battery.
Further, in recent years, in order to reduce the emission amount of carbon dioxide that is a greenhouse gas generated along with the use of fossil fuels, efforts have been made to introduce vehicles which use no fossil fuel during running, such as an electric vehicle, a hybrid vehicle using fossil fuel and a battery as a vehicle drive source to drastically improve the fuel efficiency, or a plug-in hybrid vehicle.
However, sales of such electric vehicles are currently far from strong, and are rather sluggish.
Taking the electric vehicle as an example, one of the major reasons for the sluggish sales is significant dissatisfaction with winter use from automobile users. This derives from a drawback that, when the vehicle interior is heated and the visibility of a window is secured (anti-fogging is performed) during driving in winter when outside air temperature decreases, the cruising distance is drastically decreased.
For example, there are reports that, in a case where the vehicle is driven while the interior thereof is maintained at about 25° C. when the outside air temperature is 0° C., the cruising distance decreases by about 30% as compared to the case where air conditioning and anti-fogging are not performed, and when the outside air temperature is −10° C., the cruising distance decreases by half. The consumption of energy from the battery increases in winter as described above due to adoption of a system in which low-humidity and low-temperature outside air is introduced inside the vehicle for the purpose of anti-fogging, and the introduced air is heated for heating the interior. Fogging on the glass window is mainly caused by water vapor (insensible perspiration) contained in the breath of an occupant. The amount of this water vapor is 30 to 50 g/h per adult male. If this water vapor amount can be absorbed by a dehumidifying member (desiccant), fogging on the window can be prevented.
For example, in a case where the outside air temperature is lower than the vehicle interior temperature, when electric power from an in-vehicle battery is used for heating the vehicle interior or preventing dew condensation on a glass window, the cruising distance is decreased. This cruising distance decrease phenomenon in cold weather is mainly caused by introducing low-humidity outside air from the necessity of maintaining low vehicle interior air humidity for the purpose of preventing fogging on the window during running (safety reasons), and then heating the introduced air by the electric power from the in-vehicle battery for vehicle interior heating.
Further, a compression refrigerating machine is used for vehicle interior cooling. Ina case where a dew-point temperature of the air to be processed is higher than the target room temperature, dew condensation occurs from the air to be processed when the air to be processed is cooled down to the dew-point temperature or less. Therefore, a load on the compression refrigerating machine increases, and the refrigeration efficiency in cooling down to a low temperature reduces, which leads to increase in amount of power consumption. As a result, there arise problems in that the amount of power consumption in the in-vehicle battery increases, and the cruising distance decreases.
In order to solve those problems, a measure of increasing the capacity of the battery to be mounted on the vehicle is taken to secure the cruising distance per one charging, but such a measure may lead to increase in vehicle weight and battery cost. In order to solve such problems, it is effective to realize cooling and heating without depending on much power supply from the mounted battery, or performing anti-fogging on a window with low power consumption or reducing water vapor condensation latent heat load during vehicle interior cooling.
For example, when three occupants get in a vehicle having a space with an air weight of 4.8 kg under conditions of an outside temperature of 5° C. and a relative humidity of 60% (absolute humidity of 2.6 g/kg), the amount of insensible perspiration (exuded amount of water vapor) of a human is about 30 g/h per person, and hence the absolute humidity of the vehicle interior air increases at a rate of 18.8 g/h per air of 1 kg. Therefore, dew condensation occurs on a glass window as the air temperature comes close to 5° C. in the vicinity of the glass window. The saturation water vapor amount of 5° C. air is 5.4 g per air of 1 kg. Therefore, it takes about 9 minutes at the latest from the start of driving until the relative humidity reaches 100% and the glass window starts to fog.
As measures for preventing dew condensation (fogging) on the window or the like, in recent years, there has been proposed a desiccant air conditioning technology that uses a dehumidifying member for an HVAC device for an automobile. The desiccant air conditioning technology utilizes the moisture absorbing action of the dehumidifying member. The dehumidifying member that has absorbed a certain amount of moisture needs to be regenerated by low-relative-humidity and high-temperature air. For example, Patent Literature 1 describes an air conditioning system for an electric vehicle which uses warm air from an in-vehicle heat pump to regenerate a ventilation rotor carrying the dehumidifying member.
Patent Literature 2 describes an air conditioning system in which a moisture-absorbing container containing the dehumidifying member is placed in the air conditioning system for an automobile for the purpose of reducing the load of dehumidification of the air to be processed, to thereby reduce the load of the compression refrigerating machine for cooling/dehumidification.
Further, Patent Literature 3 describes an air conditioning system which uses heat storage to additionally performs hot water production during charging of the in-vehicle battery in order to reduce the load of electric power in heating of the electric vehicle.
Further, for example, Patent Literature 4 describes a technology of arranging a dehumidifying unit including a dehumidifying member inside the vehicle to absorb water vapor exuded from an occupant by the dehumidifying member during running, to thereby prevent fogging on the window.